Residual torsions on an elongated element such as a steel cord must be controlled and thus measured during the manufacture of the elongated element. In the absence of adequate control, the downstream processing of the elongated elements such as the integration of steel cords into rubber plies may become difficult or even problematic. Indeed, uncontrolled residual torsions of steel cords may give rise to tip rise of rubber sheets reinforced with those steel cords. The automatic handling of those rubber sheets may fail as a result of this tip rise.
The prior art discloses several embodiments to measure residual torsions.
U.S. Pat. No. 4,642,979 discloses a way of adjusting the lay of a wire rope by measuring the remaining or residual torque in the wire rope. After the twisting of the wire rope, the wire rope is running in a U-portion over a wheel or dancer roller. This dancer roller is pivotally mounted. The angle of rotation of the dancer roller is measured in order to have an indication about the remaining torque on the wire rope.
This method of measuring residual torsions by measuring the rotation angle of a dancer roller that may pivot more or less freely, although widely used in practice, has several disadvantages.
When allowing the dancer roller to rotate freely, one starts to influence the parameter one want to measure, namely the free rotation starts to reduce already the number of residual torsions.
In addition, the measurement shows some hysteresis behaviour.
Moreover, practice has shown that it is difficult to cover the full range of residual torsions, despite the possibility for almost free rotation.